#17415: Creating an object with an explicit primary key value causes the next
creation to fail under PostgreSQL
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Reporter: niko@… | Owner: nobody
Type: Bug | Status: new
Component: Database layer | Version: SVN
(models, ORM) | Resolution:
Severity: Normal | Triage Stage: Accepted
Keywords: site admin create | Needs documentation: 0
db orm | Patch needs improvement: 0
Has patch: 0 | UI/UX: 0
Needs tests: 0 |
Easy pickings: 0 |
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Comment (by russellm):
I just saw this ticket go past as part of the 1.4 rundown, and it occurred
to me that the fix is obvious, and has precedence in Django's source tree.
Once you've manually created *any* object with a primary key, you need to
invoke the SQL generated by the sqlsequencereset management command. This
finds the largest PK value, and sets the sequence to select the next
available PK value. This is an issue on Postgres and Oracle, because they
both use sequences for autogenerated PKs; MySQL and SQLite both use
"largest PK + 1" internal mechanisms, IIRC.
We already do this as part of fixture loading. Loading a fixture involves
manually specifying a whole lot of primary key values; one of the last
things the loaddata command does before committing is to reset the
sequences. This ensures that the next object with an autogenerated PK
value will have a valid PK value.
From my reading, this bug would have existed for as long as the sites
framework has existed; although it would have been masked on any site that
loaded fixtures (since loading a single fixture would have reset the
sequence as a side effect).
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Ticket URL: <https://code.djangoproject.com/ticket/17415#comment:6>
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